Most traditional firearm ammunition cartridges are constructed using a metal shell casing (e.g. a brass casing). The metal casing of a traditional cartridge typically contains some amount of propellant (e.g. gunpowder, smokeless powder, etc.) in a rearward portion of the cartridge that is sometimes referred to as the cartridge “body”. The metal casing of a traditional casing also holds a projectile in a frontward portion of the cartridge that is sometimes referred to as the cartridge “neck”. Traditional metal cartridge cases typically have a tapered shape, in which a relatively wider diameter body steps down to a relatively smaller diameter neck. When a traditional metal case cartridge is fired, the propellant contained in the metal casing is ignited. Gases resulting from the burning of the propellant pressurize and expand the metal casing against the wall of the chamber, and push against the base of the brass casing, causing the projectile to be expelled from the front of the cartridge and through the barrel of the firearm.
In contrast to traditional metal case cartridges, cased telescoped (CT) ammunition cartridges completely encase the propellant and the projectile within a cylindrical shell that is made of polymer. By eliminating the relatively heavy metal casing used in traditional metal case ammunition, CT ammunition provides a significant reduction in ammunition weight, enabling relatively larger numbers of rounds to be carried per unit weight, e.g. by infantry soldiers.